*2.5. Tensile Properties of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

images (**a**,**c**).

As illustrated in Figures 5–7, the content of both HNT and TO@HNT increases the aggregation of the obtained CS/PVOH/HNT, and CS/PVOH/TO@HNT nanocomposites Typical stress-strain curves of all CS/PVOH/HNT and CS/PVOH/TO@HNT films are shown in Figure 8.

decrease further. Nevertheless, SEM images of the final nanocomposite films show that both pure HNT and TO@HNT nanohybrid were homogeneously dispersed and suggest From stress-strain curves in Figure 8 the Young's (E) Modulus, ultimate tensile strength (σuts), and % strain at break (εb) values were calculated and are listed in Table 1 for comparison.

polymer matrix compared to the incorporation of the respective pure HNT.

enhanced compatibility with the polymer matrix. Moreover, SEM surface and crosssection images were shown more homogenous dispersion in the case of TO@HNT hybrid nanostructure in nanocomposite films compared to the relevant of pure HNT. This means that the TO@HNT hybrid nanostructure was incorporated significantly better in the

shown in Figure 8.

*2.5. Tensile Properties of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

Typical stress-strain curves of all CS/PVOH/HNT and CS/PVOH/TO@HNT films are

**Figure 8.** Stress-strain curves of (1) CS/PVOH, (2) CS/PVOH/5HNT, (3) CS/PVOH/10HNT, (4) CS/PVOH/15HNT, (5) CS/PVOH/5TO@HNT, (6) CS/PVOH/10TO@HNT and (7) CS/PVOH/15TO@HNT*.* **Figure 8.** Stress-strain curves of (1) CS/PVOH, (2) CS/PVOH/5HNT, (3) CS/PVOH/10HNT, (4) CS/PVOH/15HNT, (5) CS/PVOH/5TO@HNT, (6) CS/PVOH/10TO@HNT and (7) CS/PVOH/15TO@HNT.

From stress-strain curves in Figure 8 the Young's (E) Modulus, ultimate tensile strength (σuts), and % strain at break (εb) values were calculated and are listed in Table 1 **Table 1.** Calculated values of Young's (E) Modulus, ultimate tensile strength (σuts), and % strain at break (ε<sup>b</sup> ).


CS/PVOH/10HNT 2766.0 ± 35.1 79.8 ± 1.7 5.7 ± 0.8

CS/PVOH/15HNT 2865.0 ± 27.4 96.0 ± 1.2 6.7 ± 0.6 CS/PVOH/5TO@HNT 2644.5 ± 13.4 74.9 ± 2.3 7.2 ± 2.1 CS/PVOH/10TO@HNT 2993.7 ± 27.6 103.7 ± 1.4 7.1 ± 0.2 CS/PVOH/15TO@HNT 2965.0 ± 29.4 98.5 ± 1.5 6.8 ± 0.7 From the Young's (E) Modulus, ultimate tensile strength (σuts), and % strain at break (εb) values, which are presented in Table 1, we could assume that CS/PVOH/HNT and CS/PVOH/TO@HNT nanocomposite films are stronger than pure CS/PVOH film. The higher the nominal content of the HNT and TO@HNT the higher ultimate strength and lower elongation at break values. In advance, TO@HNT-based nanocomposite films exhibited higher strength values than HNT-based nanocomposites. The increase of tensile strength with HNT and TO@HNT is in agreement with previous reports where HNT loaded in CS/PVOH with nominal content 0*–*5 wt.%. [53]. Here it is reported for the first From the Young's (E) Modulus, ultimate tensile strength (σuts), and % strain at break (εb) values, which are presented in Table 1, we could assume that CS/PVOH/HNT and CS/PVOH/TO@HNT nanocomposite films are stronger than pure CS/PVOH film. The higher the nominal content of the HNT and TO@HNT the higher ultimate strength and lower elongation at break values. In advance, TO@HNT-based nanocomposite films exhibited higher strength values than HNT-based nanocomposites. The increase of tensile strength with HNT and TO@HNT is in agreement with previous reports where HNT loaded in CS/PVOH with nominal content 0–5 wt.%. [53]. Here it is reported for the first time that this increment is existed also for higher HNT nominal loading up to 15 wt.%. It is also reported that a higher tensile increment is taking place for TO@HNT loading compared to the relevant HNT loading. This higher increase of tensile strength with TO@HNT addition is in agreement with the higher dispersion of the TO@HNT in the CS/PVOH matrix as was presented before by the XRD and SEM results.

#### time that this increment is existed also for higher HNT nominal loading up to 15 wt.%. It is also reported that a higher tensile increment is taking place for TO@HNT loading *2.6. UV-vis Transmittance of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

CS/PVOH matrix as was presented before by the XRD and SEM results.

compared to the relevant HNT loading. This higher increase of tensile strength with TO@HNT addition is in agreement with the higher dispersion of the TO@HNT in the In Figure 9 photo images (see Figure 9a) and UV-vis plots (see Figure 9b) of all prepared films are shown for comparison.

*2.6. UV-vis Transmittance of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

prepared films are shown for comparison.

In Figure 9 photo images (see Figure 9a) and UV-vis plots (see Figure 9b) of all

**Figure 9.** (**a**) photo images and (**b**) UV-vis transmittance plots of (1) pure CS/PVOH films, (2) CS/PVOH/5HNT, (3) CS/PVOH/10HNT, (4) CS/PVOH/15HNT, (5) CS/PVOH/5TO@HNT, (6) CS/PVOH/10TO@HNT, and (7) CS/PVOH/5TO@HNT films. **Figure 9.** (**a**) photo images and (**b**) UV-vis transmittance plots of (1) pure CS/PVOH films, (2) CS/PVOH/5HNT, (3) CS/PVOH/10HNT, (4) CS/PVOH/15HNT, (5) CS/PVOH/5TO@HNT, (6) CS/PVOH/10TO@HNT, and (7) CS/PVOH/5TO@HNT films.

As it is obtained in UV-vis transmittance plots and illustrated in film images the addition of both HNT and TO@HNT decreases the transmittance of films. From UV-vis transmittance plots is obtained that TO@HNT-based films exhibited higher transmittance than HNT-based films. This result is in accordance with the higher dispersity of TO@HNT hybrid nanostructure in the CS/PVOH matrix which was discussed above in XRD and SEM results. As it is obtained in UV-vis transmittance plots and illustrated in film images the addition of both HNT and TO@HNT decreases the transmittance of films. From UV-vis transmittance plots is obtained that TO@HNT-based films exhibited higher transmittance than HNT-based films. This result is in accordance with the higher dispersity of TO@HNT hybrid nanostructure in the CS/PVOH matrix which was discussed above in XRD and SEM results.
